(a) Field of the Invention
The present invention relates to a liquid crystal display, and in particular, to a vertically aligned mode liquid crystal display with a pixel region divided into several domains for obtaining a wide viewing angle.
(b) Description of the Related Art
A typical liquid crystal display (“LCD”) includes an upper panel provided with a common electrode and an array of color filters, a lower panel provided with a plurality of thin film transistors (“TFTs) and a plurality of pixel electrodes, and a liquid crystal layer is interposed therebetween. The pixel electrodes and the common electrode are applied with electric voltages and the voltage difference therebetween causes electric field. The variation of the electric field changes the orientations of liquid crystal molecules in the liquid crystal layer and thus the transmittance of light passing through the liquid crystal layer. As a result, the LCD displays desired images by adjusting the voltage difference between the pixel electrodes and the common electrode.
The LCD has a major disadvantage of its narrow viewing angle, and several techniques for increasing the viewing angle have been developed. Among these techniques, the provision of aperture patterns or a plurality of projections on the pixel electrodes and the common electrode opposite each other along with the vertical alignment of the liquid crystal molecules with respect to the upper and the lower panels is promising.
The aperture patterns provided both at the pixel electrodes and the common electrode give wide viewing angle by generating fringe field to adjust the tilt directions of the liquid crystal molecules.
The provision of the projections both on the pixel electrode and the common electrode distorts the electric field to adjust the tilt directions of the liquid crystal molecules.
The fringe field for adjusting the tilt directions of the liquid crystal molecules to form a plurality of domains is also obtained by providing the aperture patterns at the pixel electrodes and the projections on the common electrodes.
Such a vertically aligned (“VA”) mode LCD needs higher driving voltages than a twisted nematic (“TN”) mode LCD where the liquid crystal molecules have twisted alignment. In detail, the magnitude of the analogue driving voltage AVdd required for the TN mode LCD is equal to or less than 9V, while the driving voltage AVdd for the VA mode LCD is in a range between 10V and 13V. Thus, the TN mode LCD can use 10V tape carrier package (“TAP”) integrated circuits (“ICs”) as driving ICs, while the VA mode LCD is obliged to use 13V TAP ICs or 15V TAP ICs. The expensive price of the 13V TAP ICs or the 15V TAP ICs relative to the 10V TAP ICs weakens the price competitiveness.